diff --git a/grep.c b/grep.c
index f7c3a5803e..1de4ab49c0 100644
--- a/grep.c
+++ b/grep.c
@@ -388,11 +388,11 @@ static void compile_pcre1_regexp(struct grep_pat *p, const struct grep_opt *opt)
 	int options = PCRE_MULTILINE;
 
 	if (opt->ignore_case) {
-		if (has_non_ascii(p->pattern))
+		if (!opt->ignore_locale && has_non_ascii(p->pattern))
 			p->pcre1_tables = pcre_maketables();
 		options |= PCRE_CASELESS;
 	}
-	if (is_utf8_locale() && has_non_ascii(p->pattern))
+	if (!opt->ignore_locale && is_utf8_locale() && has_non_ascii(p->pattern))
 		options |= PCRE_UTF8;
 
 	p->pcre1_regexp = pcre_compile(p->pattern, options, &error, &erroffset,
@@ -498,14 +498,14 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
 	p->pcre2_compile_context = NULL;
 
 	if (opt->ignore_case) {
-		if (has_non_ascii(p->pattern)) {
+		if (!opt->ignore_locale && has_non_ascii(p->pattern)) {
 			character_tables = pcre2_maketables(NULL);
 			p->pcre2_compile_context = pcre2_compile_context_create(NULL);
 			pcre2_set_character_tables(p->pcre2_compile_context, character_tables);
 		}
 		options |= PCRE2_CASELESS;
 	}
-	if (is_utf8_locale() && has_non_ascii(p->pattern))
+	if (!opt->ignore_locale && is_utf8_locale() && has_non_ascii(p->pattern))
 		options |= PCRE2_UTF;
 
 	p->pcre2_pattern = pcre2_compile((PCRE2_SPTR)p->pattern,
diff --git a/grep.h b/grep.h
index 1875880f37..4bb8a79d93 100644
--- a/grep.h
+++ b/grep.h
@@ -173,6 +173,7 @@ struct grep_opt {
 	int funcbody;
 	int extended_regexp_option;
 	int pattern_type_option;
+	int ignore_locale;
 	char colors[NR_GREP_COLORS][COLOR_MAXLEN];
 	unsigned pre_context;
 	unsigned post_context;
diff --git a/revision.c b/revision.c
index 621feb9df7..a842fb158a 100644
--- a/revision.c
+++ b/revision.c
@@ -28,6 +28,7 @@
 #include "commit-graph.h"
 #include "prio-queue.h"
 #include "hashmap.h"
+#include "utf8.h"
 
 volatile show_early_output_fn_t show_early_output;
 
@@ -2655,6 +2656,8 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 
 	grep_commit_pattern_type(GREP_PATTERN_TYPE_UNSPECIFIED,
 				 &revs->grep_filter);
+	if (!is_encoding_utf8(get_log_output_encoding()))
+		revs->grep_filter.ignore_locale = 1;
 	compile_grep_patterns(&revs->grep_filter);
 
 	if (revs->reverse && revs->reflog_info)
diff --git a/t/t4210-log-i18n.sh b/t/t4210-log-i18n.sh
index 86d22c1d4c..515bcb7ce1 100755
--- a/t/t4210-log-i18n.sh
+++ b/t/t4210-log-i18n.sh
@@ -59,10 +59,8 @@ test_expect_success 'log --grep does not find non-reencoded values (latin1)' '
 for engine in fixed basic extended perl
 do
 	prereq=
-	result=success
 	if test $engine = "perl"
 	then
-		result=failure
 		prereq="PCRE"
 	else
 		prereq=""
@@ -72,7 +70,7 @@ do
 	then
 	    force_regex=.*
 	fi
-	test_expect_$result GETTEXT_LOCALE,$prereq "-c grep.patternType=$engine log --grep does not find non-reencoded values (latin1 + locale)" "
+	test_expect_success GETTEXT_LOCALE,$prereq "-c grep.patternType=$engine log --grep does not find non-reencoded values (latin1 + locale)" "
 		cat >expect <<-\EOF &&
 		latin1
 		utf8
@@ -86,7 +84,7 @@ do
 		test_must_be_empty actual
 	"
 
-	test_expect_$result GETTEXT_LOCALE,$prereq "-c grep.patternType=$engine log --grep does not die on invalid UTF-8 value (latin1 + locale + invalid needle)" "
+	test_expect_success GETTEXT_LOCALE,$prereq "-c grep.patternType=$engine log --grep does not die on invalid UTF-8 value (latin1 + locale + invalid needle)" "
 		LC_ALL=\"$is_IS_locale\" git -c grep.patternType=$engine log --encoding=ISO-8859-1 --format=%s --grep=\"$force_regex$invalid_e\" >actual &&
 		test_must_be_empty actual
 	"